The present invention relates to a silver halide emulsion.
More particularly, the present invention is concerned with a silver halide emulsion containing silver halide grains having a silver chloride region therein.
Further, the present invention is concerned with a silver halide photographic emulsion having high sensitivity and provided with effectual means for regulating an interlayer effect.
In the field of color photosensitive materials, especially, color reversal photosensitive materials being often employed by professional photographers, a color photosensitive material with high sensitivity is demanded for taking scene photographs such as sports photographs requiring a high shutter speed and stage photographs encountering difficulty in obtaining a satisfactory amount of light for exposure. However, the conventional highly sensitive photosensitive materials for color photography have coarse graininess, so that an improvement is desired in the relationship of sensitivity/graininess.
Various techniques can be used for enhancing the sensitivity of the silver halide emulsion. With respect to the metal doping technique, it is disclosed that conducting a grain formation in the presence of any of various metals capable of becoming a shallow electron trap (SET) in grains to thereby effect doping in the grains is effective in enhancing sensitivity, in connection with silver bromide grains in, for example, U.S. Pat. No. 4,937,180, and silver iodobromide grains and is disclosed in, for example, U.S. Pat. No. 4,945,035 in connection with a system with a composition comprising at least 50 mol % of silver chloride and up to 5 mol % of silver iodide. Moreover, U.S. Pat. No. 5,503,970 and 5,503,971 discloses that grains which have high sensitivity and are excellent in graininess and toughness can be obtained by doping ultrathin silver iodobromide grains having an epitaxial containing silver chloride formed at grain surfaces thereof, with a metal complex having a shallow electron trap.
Processes for producing tabular silver halide grains and techniques for utilizing the same are disclosed in, for example, U.S. Pat. Nos. 4,434,226, 4,439,520, 4,414,310, 4,433,048, 4,414,306 and 4,459,353. The advantages of the tabular silver halide grains are known in, for examples improving the relationship between sensitivity and graininess inclusive of enhancement of the efficiency of color sensitization by a spectral sensitizing dye.
Studies for using the tabular grains possessing the above advantages in large size regions which have an intense impact on the performance of color negative lightsensitive materials have been promoted, and conspicuous progress has been attained with respect to the tabular grains of large size regions, including the sensitivity enhancing technique by dislocation as described in, for example, Jpn. Pat. Appln. KOKAI Publication (hereinafter referred to as JP-A-) No. 63-220238.
In contrast to the lightsensitive color negative material, with regard to color reversal lightsensitive materials, what has an intense impact on the performance of the material is grains of small size regions.
With respect to the tabular grains of small size regions, JP-A-62-115435 discloses tabular grains having a diameter of 0.2 to 0.55 .mu.m and having an aspect ratio of at least 8. However, in the invention described in this publication, attention was drawn to the optical characteristics of grains, and the invention did not lead to the enhancement of sensitivity of small sized tabular grains per se.
Silver halide protrusions are disclosed in, for example, U.S. Pat. No. 5,494,789 and 4,435,501. However, there is no disclosure relating to tabular grains having an equivalent circular diameter of not greater than 0.6 .mu.m, and there has been a demand for development of a technology for enhancing the sensitivity of tabular grains of small size regions.
Interlayer effect technology for improving a color reproduction is important in the field of color photographic lightsensitive materials. With respect to conventional lightsensitive color reversal materials, the regulation of the interlayer effect has been mainly carried out by regulating the silver iodide content of grains. However, the regulation of the interlayer effect by regulating the silver iodide content of grains has a limit, and the development of more effectual means for regulating the interlayer effect has been desired.